Apparatus for mixing liquids and gases



Nov. 12, 1935.

A. J. MYHREN El l. APPARATUS FOR MIXING LIQUIDS AND GASES Filed Dec. 15,1953 m 5 A. Z a 5 J J 3 a 2 m 1 1. n .4 4 1. ll 0 l 5 2/9 4 I! W I l ORI. I W y u 5 .7 ,H 6 I a J. 5 0 2 a; l .0 Z w n "5 3 5 J J M ii W .m A WM rm m UuH W 2 P M M 1 5 m J W #3, a P

0 R w m p 5 M K 5 wm M S 5M6, WW NH EVA m IJN 5 0 Mr ATTORNEYSliquid-level (b) in the water Patented Nov. 12, 1935 UNITED STATES-2,020,850 APPARATUS FOR MIXING LIQUIDS AND cases I Arne J. Myhren andByron Marquis, Palmerton,

Pa., assignors to The New Jersey Zinc Company, New York, N. Jersey Y., acorporation of New Application December 15, 1933, Serial No. 702,579

10 Claims.

The present invention relates to apparatus for bringing liquids orslurries into intimate contact with gases, and has for its object theprovision of an improved apparatus of this character. The inventioncontemplates more particularly a novel combination of eductor-s withtanks and pumps for the circulation of liquids and gases, so arrangedthat intimate contact between the liquid and gas may be established byrepeatedly causing the liquid to entrain the gas in a number 01!eductors operated in series.

These and other objects of the invention will be more readily understoodby reference to the accompanying drawing, in which:

Fig. 1 is a diagrammatic elevation of an apparatus embodying theinvention.

Fig. 2 is a section on the line 2-2 of Fig. 1, showing in detail theconstruction of the Venturi tube eductor 6, and likewise that of theeductors 6, 6", 1,1 and 1" in Fig. 1.

The apparatus illustrated in the drawing comprises three tanks 5, 5', 5"(arranged in series), of circular cross-section and with conicalbottoms, each tank being provided with two Venturi tube eductors 6 andI, 6' and 1', and 6" and 1", respectively. The series of tanks isprovided with a gas inlet pipe 8" (entering the top portion of tank 5")and a gas outlet pipe 9 (discharging from tank 5). A gas pipe 8'connects the top portions of tanks 5" and 5' and a gas pipe 8 connectsthe top portions of tanks 5 and 5. The system of pipes 8", 8', 8 and 9connects the tanks in series at points above the normal level (a) ofliquid or slurry therein in such fashion that gas can flow freelythrough the series of tanks.

The gas outlet pipe 9 dips below the liquid-level (b) in a water sealit. The gas-space above the seal M is connected by a pipe II with thesuction side of a fan 2. The pressure side of the fan I2 is connected bya pipe I3 with a screen-box I, which contains metal screens (preferablymade oi a metal of high heat conductivity such as copper) set across thepath of the gases therethrough. The screen box H is connected by a pipel5 to a gas burner l6, provided with a stack II.

It is to be understood that the screen box It and the burner l6 are ofparticular utility-when the gas utilized is combustible. In that case,the metal screens in the box It prevent back-firing of the flame in thegas burner l6. In case the gas used is not combustible, the screen box Iand the burner "3 may be dispensed with. The water seal III is ofutility not only as a further safe-guard against back-firing, but alsoas a means of regulating the efiective suction of the fan l2. Theeffective suction of the fan I2 on the outlet pipe 9 may be increased bylowering the water-level (b) in the water seal l0, and decreased byraising the water level. Moreover, the water seal l prevents theentrance of air into the tank when the tan I2 is shut down, for examplefor the purpose of attaching a spare fan.

The tanks 5, 5' and 5" are provided with pumps for liquid and/or slurrytransport, and pipe lines 10 for liquid or slurry are appropriatelyconnected with the pumps, tanks and Venturi tube eductors in suchfashion that liquid and/or slurry can be transported through the seriesof tanks and likewise partly recirculated in the individual tanks, whilebeing brought into intimate contact with gas traversing the series oftanks in general counter-current with the liquid and/or slurry. Each ofthe six Venturi tube eductors (6, 1, 6', 'l', 6" and I") is arranged torecirculate gas through the tank with which it is operativelyassociated, while intimately mixing the gas with the liquid and/orslurry. The Venturi tube eductor 6 introduces liquid into the system bydischarging it into tank 5. The Venturi tube eductors I, and I serve torecirculate liquid or slurry through the tanks with which they areconnected (through tanks 5, 5' and 5", respectively). The Venturi tubeeductors 6' and 6" serve to convey liquid or slurry from one tank intothe next tank in the series. Thus, Venturi tube eductor 6' serves toconvey liquid or slurry (withdrawn from tank 5) into tank 5'; andVenturi tube eductor 6" serves to convey liquid or slurry (withdrawnfrom tank 5') into tank 5".

The apparatus shown in Fig. 1 will now be described in greater detail:

A pump 20 is connected on its suction side to a source of liquid (notshown). On its pressure side, the pump 20 is connected with a pipe 2|,part of which consists of the rubber hose segment 22, provided with apinch valve 23. The pipe 2| leads to the Venturi tube eductor 6. Betweenthe pinch valve 23 and the eductor 6, the pipe 2| is provided with apressure gauge 24, for indicating the rate of delivery of liquor to theVenturi tube eductor 6.

The structure of the Venturi tube eductor 6 will be more clearlyunderstood by reference to Fig. 2. The pipe 2| connects with a duct 25,in 5 which is placed a spiral baflle 26. The duct 25 terminates in adischarge nozzle 21 in a gas chamber 28, connected by a pipe 29 to theupper portion of the tank 5 (i. e., the portion of the tank 5 above theline of normal or liquid level a u therein). The nozzle 21 is placedconcentrically with a Venturi tube 30 communicating with the gas-chamber28 at a point opposite the nozzle 21.

Referring again to Fig. l, the suction side of. a

pump 3| is connected by a pipe 32 to the discharge=orifice at thetip ofthe'conical bottom of pinch valve 36, and is also provided with thepressure gauge 31, between the pinch valve 36 and the Venturi tubeeductor I. The branch pipe 2| is likewise provided with a rubber hosesection 22' equipped with a pinch valve 23', and provided with apressure gauge 24 between the pinch valve 23' and the Venturi tubeeductor 6'. It will be readily understood that the relative amounts ofliquid (or slurry) entering the branch pipes 34 and 2!, respectively,can be appropriately regulated, as as hereinafter more particularlyexplained, by appropriate adjustment of the pinch valves 23 and 35,respectively; and that the relative amounts of liquid or slurry flowingthrough the pipes 2| and 34 can be determined at any time by comparingthe reading of the gauges 24' and 31.

The structure of the Venturi tube eductors 6', I, I, etc. is the same asthat of Venturi tube eductor 6 hereinbefore described. Pipes l8, l9 andI9" I connect the upper portion of the tanks 5, 5 and 5" with the gaschambers of the Venturi tube eductors I, I and 1', respectively.

The structure and arrangement of the pump 3|, pipes 32' and 33, branchpipe 34' with the rubber hose segment 35', pinch valve 36' and gauge 31,

4o branch pipe 2|" with the rubber hose segment 22", pinch valve 23" andgauge 24", and the Venturi tube eductcrs l and 6", are the same withrespect to tanks 5' and 5" as the structure and arrangement of thecorrespondingly identified elements described with respect to tanks 5and 5.

' The pump 3|" is connected on its suction side to the pipe 32"communicating with the discharge orifice in the conical bottom of. thetank 5". The pressure side of the pump 3|" is connected to the pipe 33",which divides into the branch pipe 34" (connecting with the Venturi tubeeductor 'l") and branch pipe 38, which serves as an outlet for thedischarge of liquid or slurry from the system. The branch pipe 34" isprovided with the hose segment 35", having the pinch valve 36", and withthe pressure gauge 31". The discharge pipe 38 is provided with a hosesegment 33, equipped with a pinch valve 40. It will be understood thatthe relative amounts of liquid or slurry discharged through the pipe 38and returned to the tank 5" through the Venturi tube eductor "I' can beregulated by appropriate adjustment of the valves 40 and 36", and thatthe amount oi. liquid orslurry entering the Venturi tube eductor 1" candetermined at any time by reading the gauge The apparatus shown in thedrawing may be advantageously operated as follows:

Gas is introduced into the series of tanks through the inlet .8", and isdrawn through the tanks, the outlet pipe 9, and the water seal ID by thesuction produced bythe fan I2. The effective suction of the fan l2 canbeadjusted and regulated by suitable adjustment of the water-level b inthe 7g water-seal l0. It will be understood that whenthe liquid used inthe apparatus absorbs gas either by solution or chemical reaction, thesuction produced by the gas absorption likewise tends to draw gas intothe system through the pipe 3".

The water-seal It prevents air from entering the 5 system when the fanI2 is shut down for any reason, as for example, for the purpose ofattaching a spare fan to the gas outlet line 3.

In case a combustible gas is used, the fan l2 forces the gas through theline l3, the screen box 10 I4 and the line i5 to the gas burner II. Theproducts of combustion are removed from the burner l6 by the stack II.Back-firing of the flame from the burner it into the system is guardedagainst by metal screens (made of a 15 metal of high heat conductivity,e. g. copper) placed in the path of the gases in the screen-box I4. Thewater-seal I0 is a further. safe guard against back-firing.

Liquid is introduced (preferably continuously) 20 into the system by thepump 20, which delivers liquid to the Venturi tubeeductor 6 through thepipe 2|. The amount of liquid transported by the pump 20 through thepipe 2| can be regulated by adjustment of the pinch valve 23 on the hoseseg- 25 ment 22. The rate of flow of. liquid into the Venturi tubeeductor 6 is indicated by the pressure gauge 24, connected in the pipeline 2| at a point between the Venturi tube eductor 3 and the pinchvalve 23.

From the pipe 2i, the liquid enters the duct 25 of the Venturi tubeeductor 6. A swirling motion is imparted to the liquid flowing throughthe duct 25 by the spiral baflie 26. The swirling stream of liquid thenpasses through the nozzle 35;

21 in the form of a conical expanding jet into the gas chamber 28. Thejet traverses the gaschamber 28 and enters the Venturi tube 30, which isconcentric and coaxial with the nozzle 21. In

the Venturi tube 30, the velocity of the jet of 40,

liquid is suiilciently increased by the constriction of the Venturi tubeto create suction in the gas chamber 28. Gas is thus withdrawn from thegas-chamber 28 by the suction of the Venturi tube and by entrainment inthe Jet of 45 of gas greatly in excess of the volume of liquid; 55';

for example, the volume of gas carried through the Venturi tube eductorby the liquid may be from 30 to 50 times the volume of the liquid, oreven more.

When the gas and liquid treated by the ap- 69:-

paratus react-to form a precipitate (as for example, when the gas ishydrogen sulfide and the liquid an aqueous solution of zinc sulfate,which react to form a precipitate of zinc sulfide; or

when the gas is carbon dioxide and the liquid lime 63 water or milk oflime, which react to form a precipitate of calcium carbonate), theVenturi tube eductor 6 discharges a slurry or suspension of precipitateinto, the tank 5. It should be understood that this slurry is thentreated as a 70-.

liquid in the subsequent operations. In the continuation of thedescription hereinafter, the term liquidis used to include either aliquid or a slurry, such as is produced by the reaction of the gas withthe liquid to form a solid precipitate.

The liquid charged into the tank 5 through the Venturi tube eductor 6 iswithdrawn from the discharge orifice in the conical bottom of the tankthrough the pipe 32 by the pump 3|, which forces the liquid through thepipe 33, into the branch pipes 34 and 2|. The relative amounts of liquidflowing into these two branch pipes are regulated by appropriateadjustments of the pinch valves 36 and 23', and the pressure gauges 31and 24', respectively, indicate the prevailing pressures, and thus therates of flow, in these two branch pipes. The liquid entering theVenturi tube eductor 1 is mixed therein with gas taken from the tank 5,and then returned to tank 5. The Venturi tube eductor 1 functions withrespect to mixing the gas and liquid in the same manner as the Venturitube eductor 6. The liquid entering the branch pipe 2| passes into theVenturi tube eductor 6', which functions in the same manner as Venturitube eductor 6, which respect to mixing the liquid with gas (exceptthat, as will be evident from the drawing, the Venturi tube eductor 6draws gas through its gas-pipe 29' from the tank 5'). The Venturi tubeeductor 6' discharges liquid into the tank 5' and thus transports liquidfrom tank 5 to tank 5', and the Venturi tube eductor I returns liquid tothe tank 5.

It will be understood that in order to secure a desirable uniform andconstant fiow of liquid through the apparatus, the Venturi tube eductor6' must transfer to tank 5' an amount of liquid corresponding to thatentering the tank 5 through the Venturi tube eductor 6. The rate ofdischarge of Venturi tube eductor 6' may be suitably controlled withthis end in view by appropriate adjustment of the pinch valves 23' and36.

It will also be understood that the capacity of the pump 3| must inconsequence be adequate to pump all the liquid supplied to tank 5 bypump 20 plus the amount of liquid returned to tank 5 by the Venturi tubeeductor I.

The liquid charged into tank 5' by the Venturi tube eductor 6 isrecirculated in tank 5' through the Venturi tube eductor I andtransported to tank 5 through the Venturi tube eductor 6" in a mannersimilar to that hereinbefore described.

Liquid is withdrawn from tank 5" by the pump 3|" through the line 32",and pumped into the line 33", whence it is in part discharged from thesystem through the line 38, and in part returned to tank 5" through theVenturi tube eductor 'l". The ratio of the amount discharged through thel ne 38 to that returned to the tank 5 through Venturi tube eductor 1"is appropriately controlled by proper adjustment of the pinch valves 40and 36". This adjustment is facilitated by the fact that the readings ofpressure gauge 31" are an indication of the rate at which liquid issupplied to the Venturi tube eductor 1".

In order to secure uniform and continuous flow of liquid through thesystem, it will in general be desirable to adjust the amount of liquiddischarged from the outlet 38 so that it corresponds to the amount ofliquid fed into the system through the Venturi tube eductor 6, dueallowance being made for any change in the volume of the liquid that maybe produced in consequence of its contact with the gas; as for example,the formation of a slurry of a precipitate formed by reaction of the gaswith the liquid; the condensation of vapor from the gas, or theabsorption of mist in the liquid; or the evaporation of part of theliquid.

The apparatus of the invention permits the mixing of gases and liquidsto a controlled degree. The intensity of mixing and the duration ofcontact between liquid and gas can be con trolled by a regulation of theratio of recircula- 5 tion of the liquid through the individual tanks tothe transport of liquid from tank to tank.

The apparatus is of especial utility in the precipitation of zincsulfide by treating an aqueous solution of zinc sulfate with hydrogensulfide ac- 10 cording to our copending United States application SerialNo. 702,578 filed December 15, 1933.

In the appended claims we have used the term liquid broadly to includeslurries and the like, and by fresh liquid we mean liquid introduced 15for the first time into the tankirrespective of whether or not theliquid has been previously treated in preceding tanks in the series.

The apparatus illustrated in the drawing is susceptible of variousmodifications without departing from the principles and spirit of theinvention. While we have found pinch valves particularly convenient incontrolling the flow of liquid into the eductors, other suitable typesof valves may" be used. Ordinarily, each of the tanks 5, 5' and 5" isprovided with a liquid level indicator of any suitable type forindicating the level (a) of the liquid or slurry therein.

We claim:

1. An apparatus for effecting intimate contact between a liquid and agas comprising a tank partly filled with the liquid undergoing treatmenttherein, a Venturi tube eductor operatively associated with the tank forcontinuously charging thereinto above the liquid level therein freshliquid admixed with gas withdrawn from the tank, a second Venturi tubeeductor operatively associated with the tank for recirculatingtherethrough a certain amount of the liquid undergoing treatment thereinby charging into the tank above the liquid level therein saidrecirculating amount of liquid intimately admixed with gas withdrawnfrom the tank, and means for continuously withdrawing from the tank anamount of liquid substantially equivalent to the amount of fresh liquidcharged thereinto.

2. An apparatus for effecting intimate contact between a liquid and agas comprising a series of tanks through which the liquid and gas passgenerally in counter-current, a Venturi tube 50 eductor operativelyassociated with each tank for recirculating therethrough a certainamount of the liquid undergoing treatment therein intimately admixedwith gas withdrawn from that tank, another Venturi tube eductoroperatively associated with each tank for introducing into the tank afresh supply of liquid intimately admixed with gas, and means forwithdrawing from the last tank in the series an amount of liquidsubstantially equivalent to the amount of fresh liquid introduced intothe first tank in the series.

3. An apparatus for efiecting intimate contact between a liquid and a.gas comprising a series of tanks through which the liquid and gas passgenerally in counter-current, a conduit communicating with the bottom ofeach of said tanks and with the top of that tank and with the top of thenext succeeding tank in the series, a pump operatively included in saidconduit, means associated with said conduit for controlling the relativeamounts of liquid delivered thereby to the two tanks with which theconduit communicates, and means for withdrawing through the conduit ofthe last tank in the series an amount of liquid substantially equivalent'tothe amount of 76 fresh liquid introduced into the first tank in theseries.

4. An apparatus for eflecting intimate contact between a liquid and agas comprising a series of tanks through which the liquid and gas passgenerally in counter-current, each of said tanks having a chargingVenturi tube eductor and a recirculating Venturi tube eductoroperatively associated therewith adapted to deliver to the tank liquidintimately admixed with gas withdrawn from the tank, a conduitcommunicating with the bottom of each of said tanks and with therecirculating eductor thereof and with the charging eductor of the nextsucceeding tank in the series, a pump operatively included in saidconduit, and means for withdrawing through the conduit of the last tankin the series an amount of liquid substantially equivalent to the amountof fresh liquid introduced into the first tank in v recirculatingVenturi tube eductor operatively associated therewith adapted to deliverto the tank liquid intimately admixed with gas withdrawn from the tank,a conduit communicating with the bottom of each of said tanks and withthe recirculating eductor thereof and with the charging eductor of thenext succeeding tank in the series, a pump operatively included in saidconduit, means associated with said conduit for controlling the relativeamounts of liquid delivered thereby to the recirculating eductor and thecharging eductor with which the conduit communicates,

and means for withdrawing through the conduit of the last tank in theseries an amount of liquid substantially equivalent to the amount offresh liquid introduced into the first tank in the series.

6. An apparatus for efiecting intimate contact between a liquid and agas comprising a series of tanks through which the liquid and gas passin contact, a conduit communicating with the bottom of each of saidtanks and with the top of that tank and with the top of an adjacent tankin the series, a flexible section included in the parts of said conduitcommunicating with the tops of said tanks and a pinch valve operativelyassociated with each of said flexible sections.

7. An apparatus for effecting intimate contact between a liquid and agas comprising a series of tanks through which the liquid and gas passin contact, each of said tanks having a charging eductor and arecirculating eductor operatively associated therewith adapted todeliver to the tank liquid intimately admixed with gas, a conduitcommunicating with the bottom of each of said tanks and with therecirculating eductor thereof and with the charging eductor of anadjacent tank, and means for withdrawing from the conduit of the lasttank in the series an amount of liquid substantially equivalent to the 5amount of fresh liquid introduced into the first tank in the series.

8. An apparatus for eflecting intimate contact between a liquid and agas comprising a series of tanks through which the liquid and gas passin contact, each of said tanks having a charging eductor and arecirculating eductor operatively associated therewith adapted todeliver to the tank liquid intimately admixed with gas, a conduitcommunicating with the bottom of each of said tanks and with therecirculating eductor thereof and with the charging eductor of anadjacent tank, said conduit having flexible sections in the partsthereof communicating with said eductors, a pinch valve operativelyassociated go with each of said flexible sections, and means forwithdrawing through the conduit of the last tank in the series an amountof liquid substantially equivalent to the amount of fresh liquidintroduced into the first tank in the series. 5

9. Apparatus for intimately mixing liquids and gases comprising a seriesof closed tanks adapted to be partly filled with liquid, a conduitconnecting the bottom of each tank with the upper end portion of thesucceeding tank in the series above the liquid level therein, a pumpdisposed in said conduit, a Venturi eductor disposed in said conduitadjacent the upper end portion of the succeeding tank, means forintroducing gas into said Venturi eductor, a conduit connecting eachtank in the series with the succeeding tank in the series above theliquid level in said tanks, means for introducing fresh liquid into atleast one eductor in the series, means for introducing fresh gas into atleast one tank in the series and means for withdrawing liquid from theseries of tanks.

10. Apparatus for intimately mixing liquids and gases comprising aseries of closed tanks adapted to be partly filled with liquid, aconduit connecting the lower end portion of each tank with the upper endportion of the succeeding tank in the series above the liquid leveltherein, a pump disposed in said conduit, a Venturi eductor disposed inthe said conduit adjacent the entrance of the conduit into the upper endportion of the suc- 5 ceeding tank in the series, means for supplyingliquid continuously to the first tank inthe series, means forwithdrawing liquid continuously, from the last tank in the series, andmeansior supplying gas continuously to each Venturi eductor in theseries.

ARNE J. MYHREN. BYRON MARQUIS.

